The river was a well-kept secret until the publication six years ago of "A River Runs Through It," Norman Maclean's novella that used the Blackfoot as a metaphor for the struggles of a turn-of-the- century family. Since then, the river has taken on near-religious significance, and today anglers make pilgrimages to its banks from around the country.

But now this riparian paradise is in danger, conservationists say. Twelve miles east of this town, two mining companies have proposed to develop the largest gold mine in Montana's history, just 800 yards from the river's banks.

The Seven-Up Pete mine -- named for a 19th century prospector who favored a poker game in which seven cards are dealt face up -- would tear up eight square miles of rolling hills and grasslands over the next 25 years in a search for $1.4 billion in gold. To proceed, the mine must win environmental clearances from state authorities, which could take a year or more.

President Trump addresses nation after mass shooting at Florida SchoolWhite House

Officials of the mining venture, a collaboration between Phelps Dodge Mining Co. and Canyon Resources Corp., say it would create hundreds of well-paying jobs and infuse badly needed cash into the local economy. And they say they would use state-of-the-art technologies to protect the fragile Blackfoot ecosystem.

But local environmental and angler groups are worried about the mine's ecological legacy. No matter how careful the mine's operators are, they say, the mine will leak poisonous wastes and disrupt the Blackfoot's flow, wiping out its legendary trout runs.

"This mine is just too big, too bad and too close to the river," says Karen Knudsen of the Clarks Fork Coalition, an environmental group in Missoula. "The risk is just unacceptable."

In a state founded by the mining industry -- Montana's official seal bears the motto "oro y plata," gold and silver -- one might not expect to find much opposition to a gold mine that would pump $9 million a year into state coffers.

But opposition to mining has been building in recent years, reflecting a backlash against the hundreds of polluted, abandoned mine sites around the state and a shift in Montana's economy to tourism and recreation. Today, mining accounts for less than 1 percent of the state's jobs.

"The mine threatens to damage the area's economic vitality, which is centered on recreation," says Thomas Power, chairman of the economics department at the University of Montana at Missoula. "It's very hard to paint this as a net economic benefit."

The fight over Seven-Up Pete is particularly divisive in Lincoln, where life is just beginning to return to normal since its infamous former resident, Unabomber suspect Theodore Kaczynski, was captured by federal authorities.

Even by the standards of Big Sky country, the scope of the project is staggering. To get at the gold, buried 1,200 feet underground in trace amounts, the mining company would dismantle two pine-covered buttes, blasting and removing 980 million tons of rock.

Mine workers would pile the extracted ore in two mounds, each the size of San Francisco's Russian Hill. Over 25 years, the mounds would be drenched with 172 million pounds of cyanide to leach out the trace amounts of gold. For every ton of ore, the miners will recover 0.02 ounces of gold.

The remaining pit would be more than a mile across and deep enough to hide the Washington Monument. To keep the pit dry, the venture would have to pump 15.8 million gallons of groundwater a day, more than enough to supply the daily needs of any one of Montana's largest cities.

Mine officials argue that the cyanide leaching process poses no environmental risk because the solution is weak and breaks down quickly. Polyurethane the thickness of a nickel would line the mounds to prevent the cyanide solution from contaminating groundwater.

But opponents note that all such mines leak to some degree. One day, they fear, a pulse of cyanide will be released into the Blackfoot, leaving a wake of dead fish and other aquatic life.

The most feared long-term threat, however, is acid mine drainage, a common byproduct of mining. Rock laden with sulfur is exposed to the elements, producing large amounts of sulfuric runoff that yellows and sterilizes stream bottoms.

But Seven-Up Pete officials say that because of the area's unusual geological history, the mine site has very low concentrations of acid-producing rock. "This is a very low sulfur deposit," says Bill Snoddy, a spokesman for the joint venture. "Nature has oxidized all of it."

Another concern is how the mine would affect the flow of the Blackfoot. Opponents say it would be impossible to pump so much water so close to the river without raising water temperatures, changing the river's flow or slowly sucking it dry.

The Seven-Up Pete joint venture has gone to great lengths to win over local residents. It has donated computers to the local high school and X-ray machines to the local clinic, and it helped to insulate the local senior citizens facility.

Mine officials promise that this is just the beginning. The mine would bring 390 jobs, with an average salary of over $36,000 a year, and create about 160 secondary jobs in the surrounding area. Over the life of the mine, the venture would pay out $100 million in taxes.

"It's going to have a very positive impact on Montana and on the community of Lincoln," says Snoddy.

But opponents argue that the mine would require specialized workers, and that only about a dozen Lincoln residents are likely to be hired directly by the mine. The rest of the 390 employees would come from Helena, 50 miles away, or surrounding cities.

For 20 years, Becky Garland managed the family business, Garland's Town & Country Store, before handing over the responsibility to her sister last year. Now she works with her husband restoring parts of the Blackfoot damaged by logging.

With the help of the recreation business, Garland says, the local economy is just climbing out of a recession in the local timber industry. Aside from the worries about polluting the river, her biggest fear is that the mine would put Lincoln through yet another "boom-and-bust" cycle. "It'll be very expensive the day after they leave," she says.